The present invention relates to apparatus for weighing continuously-moving articles. The invention is particularly useful in apparatus for grading produce, such as avocados, pears, mangoes, peppers, apples, etc. and is therefore described below with respect to such an application.
Many articles of produce are now graded or classified according to weight, either because the classification is based on weight, or because the classification is based on size and there is a correlation between size and weight with respect to that particular article. One known form of grader apparatus includes a plurality of parallel lines of trays for receiving the articles to be weighed, a weighing device at a weighing station in each line, and drive means for moving the trays in each line one-at-a-time longitudinally across the weighing device in its line. The actual weighing is usually done electrically or electronically, e.g., by a load cell. In some of the known grading apparatus, however, the accuracy of the weight measurement may be affected by the position of the article within the tray; for example, in the case of long articles such as avocadoes or cucumbers, the center of gravity of the article being weighed may be sufficiently off-center so as to apply a rotary moment to the tray, such that the tray drive, or its coupling to the tray drive, may act to partially support or load the tray, which would result in the measured weight being greater or less than the true weight of the article. In other known grader apparatus, the tray, including the article to be weighed, is supported on the weighing device only for a relatively small part of the movement of the tray across the weighing device, so that the apparatus must be driven at a relatively slow speed to provide the electrical or electronic weighing device sufficient time to accurately weigh each tray and to normalize between weighing to avoid the accummulation of errors.